ML13316B905

Albrz Testing Update for NRR Final

ML13316B905
Person / Time
Site:	South Texas
Issue date:	11/13/2013
From:	Taplett K South Texas
To:	Division of License Renewal
Daily J
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Download: ML13316B905 (45)

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11/13/2013 1 SOUTH TEXAS PROJECT ALUMINUM BRONZE TESTING UPDATE November 13, 2013

11/13/2013 2 Agenda

• Introductions

• Purpose

• AlBrz Dealloying Background

• Testing Protocols

• Preliminary AlBrz Testing Results

• Future Testing Plans

• AlBrz Dealloying Program Development

• Summary

• Questions

11/13/2013 3 South Texas Project (STP) Attendees

• Michael Berg - Manager, Design Engineering

• Michael Murray - Manager, Regulatory Affairs

• Rob Engen - Manager, Engineering Projects

• Arden Aldridge - License Renewal Project Manager

• Ken Taplett - Supervisor, Licensing

• Matthew Hiatt - Aluminum Bronze Project Engineer

• Fred Puleo - Licensing Engineer

• Richard Kersey - Supervisor, Civil Design Engineering

• Cong Pham - Supervisor, Mechanical Design Engineering

• Kevin Regis - ECW System Engineer

• Aaron Heinrich - Aluminum Bronze Program Engineer

• Suryakant Sam Patel - Contractor

• Russ Cipolla - Contractor, Intertek AIM (Aptech)

11/13/2013 4 Purpose

• Describe the progress of testing completed by STP on aluminum bronze components in support of License Renewal activities

• Describe the future testing scope to be completed by STP in 2014

• Describe development of program procedure to manage and analyze aluminum bronze dealloying

11/13/2013 5 AlBrz Dealloying Background

• Metallurgy

• Aluminum bronze alloy is composed of alpha, beta and gamma-2 phases depending on aluminum content and heat treatment

• Gamma-2 phase and beta phase preferentially corrode and leach out aluminum. Result is a porous structure that can result in a through-wall leak if gamma-2 or beta network is

• Typical Microstructure continuous through material

• A - copper-rich alpha matrix

• Heat treatment for castings

• B - alpha-gamma2 eutectoid

• C - isolated, preferentially attacked gamma-2 (dark determines if network is regions within the eutectoid and along the grain boundaries) continuous and whether alpha+gamma-2 eutectoid or alpha+beta eutectoid forms

11/13/2013 6 AlBrz Dealloying Background (continued)

• Dealloying Propagation

• There is a discontinuity in microstructure at the boundary between dealloyed regions and undealloyed regions in a component. This discontinuity in microstructure can be explained by the dealloying process which slowly proceeds across the component pressure boundary. As the corrosion process created by the wetted surface extends through the thickness, the Al-Brz continues to dealloy along the wetted path. The remaining wall thickness is not affected by the corrosion process until it contacts the corrosive environment. The boundary between the two material states (dealloyed / undealloyed) is not very wide and defines the depth of the dealloying in the specimen.

• Dealloying is measured / identified by etching surfaces with silver nitrate - darker regions denote dealloyed areas

• Degree of dealloying (% dealloying) is a geometrical measure

• = Depth of dealloying / component wall thickness OR

• = Area of dealloying / total component cross-sectional area

11/13/2013 7 AlBrz Dealloying Background (continued)

• Essential Cooling Water (ECW) System is constructed of aluminum bronze alloys

• SB169 CA614

• Wrought, single-phase alloy, 6.0 - 8.0% Al by weight

• Used for pipe, fittings and small-bore valves

• Not susceptible to dealloying

• SB148/271 CA 952/954

• Cast, alpha+beta+gamma-2 phase

• CA952 - 8.5%-9.5% Al by weight,

• CA954 - 10.0-11.5% Al by weight

• Used for fittings, large-bore valves, pumps

• Susceptible to dealloying

11/13/2013 8 AlBrz Dealloying Background (continued)

• History at STP

• Dealloying initially identified at STP during plant construction/start-up through large number of leaking small-bore cast fittings

• All small-bore (< 3 NPS) castings have been replaced with wrought

• Established methods to evaluate through-wall leaks in large-bore castings for operability/structural integrity

• Captured in UFSAR Appendix 9A and supporting calculations

• Long-term management by Leak-Before-Break

• Number of Through-Wall Leaks per Year

• Large-bore castings 5/yr at startup, 1-2/yr currently

11/13/2013 9 AlBrz Dealloying Background (continued)

• Susceptible Component Population

• Large bore (3 NPS) castings

• 251 flanges, 1 reducer, 1 cap, 1 elbow and 19 tees

• Bulk of through-wall leaks have been at flanges

• 151 valves and 12 pumps

• Welds or weld-repairs with susceptible weld filler material

• Mostly above and below ground piping butt-welds

• Small number of weld repairs on extruded tees and socket weld metal on some 1/2 root valves

• Non-Susceptible Component Population

• All pipe is wrought

• All below-grade fittings are wrought

• All small-bore (<3 NPS) components were replaced with wrought in 1988-1990 timeframe

• Most large-bore castings that leaked were replaced with wrought

• Some leaking valves were replaced with cast material

11/13/2013 10 AlBrz Dealloying Background (continued)

• STP has procured large number of non-susceptible spare fittings and valves to enable rapid replacement of leaking components when identified

• Replacement flanges and other fittings are wrought AlBrz

• Avoids cracking problems with welding SS fitting to AlBrz pipe

• Replacement valves are stainless steel

• Design changes for valves are in process; some will be replaced with cast AlBrz until stores are exhausted

• STP has pursued NDE techniques to characterize dealloying in-situ

• Zero-degree and Phased-array UT can detect and characterize dealloying under optimal conditions

• Continued development is ongoing but is not expected to be viable in near future

11/13/2013 11 AlBrz Dealloying Background (continued)

• Analytical models for evaluating structural integrity based on ASME Section XI and GL 90-05

• ASME Section XI Appendix H 1989

• Basic model assumes dealloyed flaw region (identified from through-wall leak) has zero strength or fracture toughness and uses conservative values for material properties

• During License Renewal, NRC challenged underlying basis for analytical model as limited test data was used to construct and validate analytical model

• Mechanical properties, dealloying flaw length correlation based on outside diameter flaw length, and other factors used in analytical model based on small sample size

• Only one dealloyed component was bend/pressure tested to validate model predictions

11/13/2013 12 Testing Protocols

• Analysis Confirmatory Test (ACT)

• Pressure Test (hydro)

• Bend Test

• Comparison of actual stress applied to the component compared to the critical bending stress predicted by the model

• Inspection of sample for chemistry, mechanical properties, microstructure, degree of dealloying, and/or cracking

• Profile Examination (PE)

• Sectioning of component to map dealloying progression

• Correlation of observed outside diameter (OD) flaw length with flaw length at mean radius of component

• Inspection of sample for chemistry, mechanical properties, microstructure, degree of dealloying, and/or cracking

11/13/2013 13 Testing Protocols (continued)

• NRC requested a total of 9 ACTs and 22 PEs to provide reasonable basis that aluminum bronze components could perform intended function during period of extended operation

• STP was credited for 1 ACT and 8 PE exams performed in the 1990s

• NRC recommended ACTs be 3 components each in 3 different sizes

• NRC recommended that a valid ACT would require a minimum level of dealloying degradation

11/13/2013 14 Testing Protocols (continued)

• STP identified 18 cast components for testing

• Only 3 of the 18 had been identified as leakers

• Remaining components were selected based on potential of finding dealloying in those locations (i.e. same component in different train had dealloyed previously, stagnant flow conditions, etc.) and accessibility

• Components were removed during ECW System drain-downs to minimize unavailability impact on system

• 2 components removed in 2012 and 4 removed in early 2013 were part of initial test scope

• PE and ACT have been or will be performed on all components

11/13/2013 15 Preliminary AlBrz Testing Results

• All results are considered Preliminary as Final QA verification has not been completed on reports

• Testing performed by Intertek (Aptech) and subcontractors under Appendix B program

• Aptech was heavily involved with AlBrz testing and analysis during plant start-up and through 1990s

• Aptech is highly experienced in material testing and ASME Section XI flaw evaluations

11/13/2013 16 2013 Testing Completed To Date

• ACT (bend test + hydro) and PE (sectioning and etching) completed on:

• 2 - 4 globe valves*

• 1 - 10 WN flange**

• 1 - 8 WN flange

• 2 - 3 WN flanges

• Through-wall leakers with no crack

• ** Through-wall leaker with crack

• Mechanical/chemical testing was not performed on every sample due to combinations of:

• Lack of dealloying

• Dealloyed area too small to fabricate test specimens

• Microstructure examination performed on selected components to ensure dealloying continues to propagate as bimetallic area

11/13/2013 17 Valve Bend Test

11/13/2013 18 Valve Bend Test Results Analysis Confirmatory Test for 4-inch Valves 80 4-Inch NPS 70 D = 4.5" t = 0.237" 60 Critical Bending Stress, (ksi)

Actual test bending 50 stress 40 30 Failure Line 20 Bend Test Max Pipe Stress Predicted bending Leakage Length Analytical 10 stress to fail Flaw Length component 0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 TW Degradation Length, (inches)

ASME Section XI Service Loading Calculated Appendix H Condition Margin Required Margin (SF)

Level B (Upset) 54.2 2.77 Level D (Faulted) 44.2 1.39

11/13/2013 19 Valve Pressure Test

11/13/2013 20 Valve Pressure Test Results Pneumatic Pressure Test Initial Final Hold Time Visible Valve Pressure Pressure (min) Leakage (psi) (psi) 100 5 100 No Leaks EWFV-6936 151 5 151 No Leaks 100 5 100 No Leaks EWFV-6937 154 5 154 No Leaks Hydrostatic Pressure Test Initial Final Hold Time Visible Valve Pressure Pressure (min) Leakage (psi) (psi) 500 1140 345 No Leak EWFV-6936 500 5 500 No Leak 500 1200 203 No Leak EWFV-6937 500 180 487 No Leak Note: Design Pressure = 120 PSI / Operating Pressure = 80 PSI Pressure Margin is approximately 4:1

11/13/2013 21 Flange Bend Test 10 flange undergoing bend test

~0.88 long crack placed in area of max tensile stress

11/13/2013 22 Flange Bend Test Stable crack tearing during Plug-like dealloying failure. Failure initiated around crack location from original crack location

11/13/2013 23 Flange Bend Test Results 10-inch NPS D = 10.75 t = 0.365 Notes:

• Structural Margin only calculated for 10 flange ASME Section since others did not have OD flaws to evaluate Service Loading Calculated XI Appendix H Condition Margin Required Margin

• Model Dealloying Length is based on AES-C-(SF) 1964-5 Fig. 4-1 Level B (Upset) 16.1 2.77

• Actual TW Dealloying Length is based on examination of fracture surface at mid-wall Level D (Faulted) 14.8 1.39

11/13/2013 24 Flange Pressure Test Leakage at existing crack location during hydro of 10 flange

11/13/2013 25 Flange Pressure Test Results Note: Design Pressure = 120 PSI Pressure Margin is approximately 2.3:1

11/13/2013 26 ACT Testing Summary

• All tested components were able to support a bending stress greater than the predicted bending stress

• All components were able to hold a pressure without failure of at least 2x design pressure

• All components had substantial structural margins (structural capacity greatly exceeded ASME required Structural Factors)

• 3 of the 6 tested components had minimal dealloying but supported loads in excess of critical stress for pre-service components

11/13/2013 27 Profile Exam Results

11/13/2013 28 Profile Exam Results

11/13/2013 29 Profile Exam Results ID# Description Max % Avg % Dealloying Character Crack 2c to 2d DA DA (Plug / Layer) (Y/N) Correlation Valid?

F-261 3 150# FF WN Flange 21.0 ~5% Plug. Narrow, isolated dealloyed N N/A regions F-169 3 150# FF WN Flange 39.2 ~5% Plug. Narrow, isolated dealloyed N N/A regions F-059 8 150# FF WN Flange 22.0 ~5% Plug. Narrow, isolated dealloyed N N/A regions F-064 10 150# FF WN Flange 100.0 ~40% Plug with more extensive Y Y dealloyed areas. Limited axial extent. One crack (~0.88 on OD, ~2.75 on ID)

V-037 4 150# Globe Valve 100.0 ~40% Plug with more extensive N N/A dealloyed areas. On both inlet/outlet flanges and throughout valve body V-041 4 150# Globe Valve 100.0 ~40% Plug with more extensive N N/A dealloyed areas. On both inlet/outlet flanges and throughout valve body Notes:

• DA = dealloying

• Avg % Dealloying is estimated, actual average not available yet

• Max % DA is a local maximum at varying circumferential cuts

• OD crack angle to through-wall dealloying angle (2c 2d) correlation is from Aptech AES-C-1964-5

11/13/2013 30 Profile Exam Summary

• Minimal dealloying on 2 - 3 flanges and 8 flange

• More extensive dealloying present on both valve bodies and 10 flange

• Existing correlation for OD crack length to TW flaw length is supported from 10 flange data

• Dealloying is plug-like with through-wall leakage occurring before average dealloying % reaches ~60%

away from the through-wall flaw

11/13/2013 31 Mechanical Testing Completed To Date

• Tensile Test

• Yield (Sy) and Ultimate (Su) Strength

• Yield by 0.2% Offset (OS) and 0.5% Extension Under Load (EUL) methods

• Typically ductile materials are measured by 0.5% EUL

• Note some older tests did not calculate yield, only ultimate strength

• Crack Tip Opening Displacement (CTOD) Test

• Fracture Toughness (KCTOD or KIC)

• Specimens

• Mix of CA954/952 material, ~24 tensile and ~25 CTOD specimens

• Pump casing, 4 globe valve body, cast tees, small-bore fittings

• Flanges were wrong geometry/thickness to produce acceptable test specimens

• Specimens were all sub-size (but standard)

• Sub-sized specimens are more subject to casting flaws/voids that dont affect macroscopic properties of larger specimens

• True values for Sy, Su, and KCTOD for dealloyed material are likely higher than reported test values

11/13/2013 32 Mechanical Properties

• Pre-service Material Properties

• Specified Minimum Strengths CA-952 CA-954 Sy (ksi) 25 30 Su (ksi) 65 75

• Models conservatively use strength of CA-952 for analysis

• CMTR for as-fabricated material typically reports higher yield and ultimate strengths

• Fracture Toughness

• Not specified as part of material specification

• Previously determined from STP test data in 1980s to be in the range of 63.5 - 95.1 ksi in1/2

• Conservatively taken as 65 ksi in1/2 in analytical models

11/13/2013 33 Test Specimens CTOD Specimen Tensile Specimen

11/13/2013 34 Tensile Test Results - Yield Strength 0.2% Offset Yield Strength Data for Al-Brz at Room Temperature 70 Small Bore Fittings (Bechtel 1988) (CA954) 8-inch Pump Shaft Casing Heat 24900 (CA954) 8-inch Pump Shaft Casing Heat 25838 (CA954) 60 4-inch Valve EWFV-6936 (CA954) 4-inch Valve EWFV-6937 CA954) 10x10x6 Tee Piece #3 (CA952) 10x10x6 Piece #4 (CA952) 50 10x10x4 Tee (CA952)

Yield Strength, Sy (ksi) 40 30 20 10 0

0 10 20 30 40 50 60 70 80 90 100 Percent Dealloying, %DA

11/13/2013 35 Tensile Test Results - Yield Strength 0.5% EUL Yield Strength Data for Al-Brz at Room Temperature 80 8-inch Pump Shaft Casing Heat 24900 (CA954) 8-inch Pump Shaft Casing Heat 25838 (CA954) 70 4-inch Valve EWFV-6936 (CA954) 4-inch Valve EWFV-6937 (CA954) 10x10x6 Tee Piece #3 (CA952) 60 10x10x6 Tee Piece #4 (CA952) 10x10x4 Tee (CA952)

Yield Strength, Sy (ksi) 50 40 30 20 10 0

0 10 20 30 40 50 60 70 80 90 100 Percent Dealloying, %DA

11/13/2013 36 Tensile Test Results - Ultimate Strength Ultimate Tensile Strength Data for Al-Brz Castings at Room Temperature 120 Small Bore Fittings (Bechtel 1988) (CA954) 110 8-inch Pump Shaft Casing Heat 24900 (CA954) 8-inch Pump Shaft Casing Heat 25838 (CA954) 100 4-inch Valve EWFV-6936 (CA954)

Ultimate Tensile Strength, Su (ksi) 4-inch Valve EWFV-6937 (CA954) 90 10x10x6 Tee Piece #3 (CA952) 10x10x6 Tee Piece #4 (CA952) 80 10x10x4 Tee (CA952) 70 60 50 40 30 20 10 0

0 10 20 30 40 50 60 70 80 90 100 Percent Dealloying, %DA

11/13/2013 37 CTOD Test Results K-CTOD (Pmax Data) vs Percent Dealloying on Uncracked Section (Properties Adjusted for Specimen %DA) 120 Small-Bore Valves (CA954) 110 8-inch Pipe Casing Heat 24900 (CA954) 8-inch Pipe Casing Heat 25838 (CA954) 100 4-inch EWFV6937 Inlet Flange (CA954)

Fracture Toughness, KCTOD, (ksi in1/2) 10x10x6 Tee Piece #4 (CA952) 10x10x6 Tee Piece #11 (CA952) 90 10x10x4 Tee (CA952)

Regression Fit 80 70 60 50 40 30 20 10 0

0 10 20 30 40 50 60 70 80 90 100 Percent Dealloying, %DA

11/13/2013 38 Mechanical Testing Summary

• Material retains strength and ductility in dealloyed state

• Ultimate strength asymptotically approaches ~30 ksi as %

dealloying increases

• Yield strength asymptotically approaches ~28 ksi as %

dealloying increases

• Material retains fracture toughness in dealloyed state

• Fracture toughness falls into the 25-30 ksi in1/2 as % dealloying approaches 100%

• Material retains ability to resist crack propagation

• Values for 100% dealloyed ultimate strength (30 ksi) and pre-service fracture toughness (65 ksi in1/2) are consistent with values used in previous analyses

• Samples with 20-25 years of aging have same properties as original samples given the same level of dealloying

11/13/2013 39 Chemical Testing/Micrography Results

~11% Al

~4% Al

11/13/2013 40 Chemical Testing/Micrography Results

~9.5% Al

~0% Al

11/13/2013 41 Chemical Testing/Micrography Summary

• Dealloyed regions are low in aluminum and undealloyed regions have aluminum content consistent with CMTR chemistry

• Reflects corrosion of high Al-content gamma-2 and/or beta phases in dealloyed regions

• Alpha phase grains are intact in both regions but have deposited Cu in dealloyed regions from corroded eutectoid

• Chemical testing and SEM examination validates use of visual methods (surface etching) for characterizing depth of dealloying as chemistry corresponds to visual indications

11/13/2013 42 Future Testing Plans

• STP intends to continue testing of AlBrz components in early 2014

• 11 components are currently planned for removal and testing between October 2013 and February 2014

• 3 - 4 WN flanges

• 4 - 6 WN flanges

• 1 - 6x6x6 tee

• 2 - 8 WN flanges

• 1 - 10 WN flange

• Components will be tested (ACT and PE) regardless of presence of leaks or % dealloying

• As opportunity presents, additional tensile and CTOD specimens will be selected for testing to build out material property curves

11/13/2013 43 Dealloying Program Procedure Development

• STP is in process of developing AlBrz Dealloying Management Program procedure

• Addresses Aging Management concerns by trending results of destructive testing and specifies destructive testing for future components

• Provides consistent, clear guidance on applying previously developed methods for structural integrity evaluations, operability reviews and relief requests

• Provides guidance on selecting NDE methods for examining dealloyed components

• Provides repository and reference for numerous reports, calculations and correspondence that support dealloying licensing basis

• Expected to be complete in early 2014

11/13/2013 44 Summary

• All testing completed to date indicates that analytical models for managing and dealloying are conservative

• Leak-before-break remains valid method for managing dealloying

• All components had substantial structural margins

• Material properties appear to only be affected by dealloying percentage, not component age

• STP proceeding with test plan in 2014 to obtain requisite number of ACT and PE tests

• STP is developing aluminum bronze dealloying management program

11/13/2013 45 Questions?